Spawning time, spawning frequency, and spawned egg number in a multiple-spawning fish, the honmoroko Gnathopogon caerulescens

The small cyprinid honmoroko Gnathopogon caerulescens is an endemic species of Lake Biwa, Japan, and a commercial resource for fisheries and aquaculture. In a laboratory setting, using eggs collected in the field, we investigated the relationship between the date of hatching of five successive cohorts of this fish and certain spawning parameters of each cohort at adulthood. Depending on the cohort, adult females spawned on average 3,000-4,000 eggs apiece in 1.5-3.5 mean spawning events between early April (water temperature 10.5℃) and mid-July (25.9℃). Spawning occurred at intervals of 3 to 9 days in May and June in one cohort, but irregularly in the other cohorts. More than 80% of the eggs released were spawned early in the breeding season (at